This invention relates to a novel synthetic porous crystalline material, ITQ-12, to a method for its preparation and to its use in catalytic conversion of organic compounds.
Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous crystalline metallosilicates having a definite crystalline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels or pores. These cavities and pores are uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as xe2x80x9cmolecular sievesxe2x80x9d and are utilized in a variety of ways to take advantage of these properties.
Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline silicates. These silicates can be described as a rigid three-dimensional framework of SiO4 and Periodic Table Group IIIA element oxide, e.g., AlO4, in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total Group IIIA element and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing the Group IIIA element is balanced by the inclusion in the crystal of a cation, for example an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of the Group IIIA element, e.g., aluminum, to the number of various cations, such as Ca/2, Sr/2, Na, K or Li, is equal to unity. One type of cation may be exchanged either entirely or partially with another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given silicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic zeolites. Many of these zeolites have come to be designated by letter or other convenient symbols, as illustrated by zeolite A (U.S. Pat. No. 2,882,243); zeolite X (U.S. Pat. No. 2,882,244); zeolite Y (U.S. Pat. No. 3,130,007); zeolite ZK-5 (U.S. Pat. No. 3,247,195); zeolite ZK-4 (U.S. Pat. No. 3,314,752); zeolite ZSM-5 (U.S. Pat. No. 3,702,886); zeolite ZSM-11(U.S. Pat. No. 3,709,979); zeolite ZSM-12 (U.S. Pat. No. 3,832,449), zeolite ZSM-20 (U.S. Pat. No. 3,972,983); ZSM-35 (U.S. Pat. No. 4,016,245); zeolite ZSM-23 (U.S. Pat. No. 4,076,842); zeolite MCM-22 (U.S. Pat. No. 4,954,325); and zeolite MCM-35 (U.S. Pat. No. 4,981,663), merely to name a few.
Although most frequently encountered in aluminosilicate form, many zeolites are known in silicate and borosilicate forms. For example, silicalite is a silicate form of ZSM-5 and is disclosed in U.S. Pat. No. 4,061,724, whereas AMS-1B is a borosilicate form of ZSM-5 and is disclosed in U.S. Pat. No. 4,269,813. In addition, GB-A-2,024,790 discloses borosilicate forms of zeolite beta (boralite B), ZSM-5 (boralite C) and ZSM-11 (boralite D).
Many zeolites are synthesized in the presence of an organic directing agent, such as an organic nitrogen compound. For example, ZSM-5 may be synthesized in the presence of tetrapropylammonium cations and zeolite MCM-22 may be synthesized in the presence of hexamethyleneimine. It is also known from U.S. Pat. No. 5,785,947 that zeolite SSZ-32 can be synthesized in the presence of N,Nxe2x80x2-diisopropylimidazolium hydroxide.
It is also known to use fluoride-containing compounds, such as hydrogen fluoride, as mineralizing agents in zeolite synthesis. For example, EP-A-337,479 discloses the use of hydrogen fluoride in water at low pH to mineralize silica in glass for the synthesis of ZSM-5.
The present invention is directed to a novel porous crystalline material, ITQ-12, having, in its calcined form, an X-ray diffraction pattern including values substantially as set forth in Table I below.
The invention further resides in a method for preparing ITQ-12 and in the conversion of organic compounds contacted with an active form of ITQ-12.